1. Field of the Invention
The present invention relates to a display device having enhanced touch sensing ability.
2. Discussion of the Related Art
Recently, a touch panel has been used as an input unit of a flat panel display device in order to allow a user to directly input information, using a finger or a pen.
Structures of a touch panel built in a flat display device include on-cell type, in-cell type, and hybrid in-cell type structures. A display device using an in-cell type touch panel or a hybrid in-cell type touch panel is referred to as a “touch panel built-in display device”. Methods for driving a touch panel include resistive and capacitive driving methods. The capacitive driving method is classified into a self cap driving method and a mutual driving method. In the case of a display device using the self cap driving method, a plurality of touch electrodes is formed on a display panel. A touch drive signal is applied to each touch electrode in order to determine whether or not touch is made.
In a conventional display device, which uses the above-mentioned self cap driving method, however, the touch electrode, to which a touch drive signal is input, is also used as a common electrode in an image display period. For this reason, the touch drive signal (square voltage waveform) applied to the touch electrode is influenced by noise generated in the display panel. Such noise may cause degradation of performance of the touch panel. Therefore, such noise should be eliminated.